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"S" shaped curved shooting a back set
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=45569		 Page 1 of 1
Author:  Colin North [ Mon Apr 20, 2015 12:37 pm ]
Post subject:  "S" shaped curved shooting a back set
I recently jointed a back set of EIR with curved grain, sort of ((())) when book matched.
Did a back bevel, 10 degrees (using a Record no.5), so equivalent to 55 degrees blade pitch, as I had a few problems getting a clean cut when joining my last set (which was Bubinga)
Set the mouth fairly tight (about 1/20th) and the chipbreaker very close to the cutting edge.
Shooting this set, the cut was a little bit cleaner, but very quickly tended to become "S" shaped, concave at the start and convex after the middle to the end. Never had the problem before.
Got there in the end, but took more time than I would like, and I have a few more sets like this.
I can only think/assume that the grain of the wood was pulling the blade/plane in at the start, then pushing it out as the grain's curve reversed.
Can someone tell me is my assumption more or less correct, and if so, will increasing the blade pitch reduce this tendency to follow the grain?
If so, what pitch would you recommend?
And will closing the mouth up very tight help?
Author:  Joe Beaver [ Mon Apr 20, 2015 2:40 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
I did encounter a similar set that I just couldn't get right with my plane, but mine is a record No. 4. I gave up on it and just made straight cuts on the table saw then finished up with 220 paper glued to the saw table. It came out OK.

I think with your No 5 someone should be able to help you get the settings/technique you need to get ur done.
Author:  Bryan Bear [ Mon Apr 20, 2015 2:50 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
This is a shot in the dark and likely not the issue but what the heck. . . Once I was getting a crazy crooked line when I was shooting a joint with a number 5. I eventually figured out what it was. The pieces ere not rectangular and the way they were registering on my shooting board made the overhang not perfectly parallel to the shooting board. unbeknownst to me, the edge of the shooting board was only slightly contacting the tail of the plane sole when I started my strokes. I didn't feel it (even though it was happening quite literally right under my nose). Essentially, I was starting each cut with a non flat sole until it moved past the interference and began to register on the plate itself; so the plane geometry was changing.
Author:  meddlingfool [ Mon Apr 20, 2015 3:30 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
Your blade might not be sharp enough, or taking too deep a cut. Whenever I get a piece like that, I just finish up with paper on the jointer bed...
Author:  kencierp [ Mon Apr 20, 2015 4:27 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
Some times sh** happens -- we use a power jointer, still once in a while we have to scratch our heads, but we get on with it, moving forward quickly by using a shooting board like this:

http://kennethmichaelguitars.com/Jointi ... alves.html
Author:  Hesh [ Mon Apr 20, 2015 5:51 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
+1 to that Ed said, I suspect that the plane could be maybe a bit sharper.
Author:  dzsmith [ Mon Apr 20, 2015 6:32 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
I had that a similar experience: my wood was not seasoned properly and the stuff was moving while I worked it.
Used the table saw and the edge was straight after the cut, but not after a few hours.
Drove me nuts till I figured it out.
Author:  Pmaj7 [ Mon Apr 20, 2015 6:48 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
I had that happen with a crazy wavy set of walnut once. I probably planned off a half of an inch on each side! I think I got it close, and finished off with a little sanding.

Sharper blade and thinner shavings are better of course. Good question about the angle. I've never tried a back bevel or different angles before, but good thinking!
Author:  alan stassforth [ Mon Apr 20, 2015 8:00 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
you could glue some sandpaper to a long level, 80 grit,
put the wood on a piece of 1/4" plywood, overhanging a bit,
lay it on a flat surface, then go at it.
That's how I join all my backs and sides!
Your problem is you're fighting the grain, then not.
Alan
Author:  Trevor Gore [ Mon Apr 20, 2015 8:19 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
Colin North wrote:
Shooting this set, the cut was a little bit cleaner, but very quickly tended to become "S" shaped, concave at the start and convex after the middle to the end. Never had the problem before.

I've never bothered to examine the profile in detail, but certainly with cranky wood I've had joints that wont fit when planing with a continuous stroke.
Colin North wrote:
I can only think/assume that the grain of the wood was pulling the blade/plane in at the start, then pushing it out as the grain's curve reversed.

That's what I put it down to. On single () shapes, get close then finish by cutting from the center out. (Not as hard as you might think). On really difficult stuff I've used a high angle block plane in short cutting strokes. Very sharp and very fine obviously helps. I've never had to resort to sanding, yet. Once you know how to get around the problem it shouldn't take more than a couple minutes longer.

This one had grain curling every which-way, but was joined with a plane (or two!). The back's the same.
Attachment:
Front_s.jpg


(All thicknessed with planes, too.)
Author:  DennisK [ Mon Apr 20, 2015 8:45 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
Has anyone tried a scraper plane for jointing? I don't have one, but it seems like a good way to get that last little bit when dealing with crazy grain.
Author:  bobgramann [ Mon Apr 20, 2015 9:21 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
Whenever I have a jointing issue, I sharpen the plane. That usually takes care of it. I do use a back bevel for really hard woods. I do sometimes plane just the high spots until it's very, very close and finish off with one full stroke to finish out.
Author:  Trevor Gore [ Mon Apr 20, 2015 9:34 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
DennisK wrote:
Has anyone tried a scraper plane for jointing? I don't have one, but it seems like a good way to get that last little bit when dealing with crazy grain.

Not scraper, but high angle, certainly. Either bevel up (Veritas) or bevel down types (modified #6). But not back-beveled (never had to, because I have the other planes).
Author:  Colin North [ Tue Apr 21, 2015 3:59 am ]
Post subject:  Re: "S" shaped curved shooting a back set
Thanks guys.
I appreciate all your input.
Just a little bit cranky grain I guess, got it by "selective" planing eventually (hit the bits that stick out)
I think the clue was that if I flipped the set, the "S" shape reversed too, it went back to concave near too me, convex for the furthest away half.
I'm still working on technique of course, but getting a bit better. Don't really want to resort to abrasives for jointing if I'm not absolutely stuck.
Sharpening -
Well I feel like most of the past 5 years I've spent learning to sharpen, theory and practice.
And I am starting to get there. I think the hairs on my left arm will soon start popping off automatically when I think about sharpening something,
For jointing, I hone to 8,000/10,000, a few swipes first with a no.7 to rough it out.
Then a freshly honed no.5 (a 62 for softwoods), advance the blade slowly until it cuts, back off slightly then advance again to thinnest possible shaving which stays together. The whole session I only reduced the total width of the set by about 4/5 mm maximum.
I think I'll play around a bit with the cutting angle, try 60/65, mainly for cleanness of cut, and close up the mouth too, and continue trying to read/feel the wood as best I can. I'm not making model trains after all.
Must have been "interesting" woods to work with there Trevor, thanks for the suggestion about the high angle block plane.
It's just part of learning process of working with dead trees! :)
Author:  Jimmyjames [ Wed Apr 22, 2015 7:57 am ]
Post subject:  Re: "S" shaped curved shooting a back set
This may have been said already. I've noticed that some parts of a board are harder and some softer which makes the plane cut easily in the soft parts and less easily in the hard while using equal amounts of pressure. I just account for it while planing by varying my pressure across those parts. Works well.

-j
Author:  Pat Hawley [ Wed Apr 22, 2015 8:52 am ]
Post subject:  Re: "S" shaped curved shooting a back set
I recently bought the Veritas Shooting Sander: http://www.leevalley.com/en/Wood/page.a ... at=1,42500
I've only shot a few backs but, so far, I find it works very easily and well. Much easier, for me anyway, than using a plane. I'm also surprised at the number of times I've used it just as a very flat sanding bar. It's a good tool.

Pat
Author:  kencierp [ Wed Apr 22, 2015 1:48 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
I'll be darn! That's pretty slick -- I imagine its easy to change paper too. Neat tool.
Author:  Pmaj7 [ Wed Apr 22, 2015 9:45 pm ]
Post subject:  Re: "S" shaped curved shooting a back set
Cool! Too bad it doesn't come in a 24".
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